High-altitude Nuclear Detonation

A high-altitude nuclear detonation is the explosion of a nuclear device at altitudes sufficiently high that blast and ground effects are negligible, but electromagnetic and radiation effects dominate. Such detonations can produce a high-altitude electromagnetic pulse (HEMP), intense nuclear radiation, thermal radiation, and long-lasting disturbances to the ionosphere and near-Earth space environment. Unlike kinetic or directed-energy attacks, high-altitude nuclear detonations can affect multiple space and ground systems simultaneously over continental scales.

Electromagnetic pulse effects are of particular concern for space systems. The extremely rapid rise time of a high-power EMP can induce very large transient voltages and currents in unprotected electrical circuits, leading to degradation or destruction of sensitive satellite electronics. In the space environment, these effects may be compounded by prompt radiation and thermal radiation that are not attenuated by the atmosphere, with damage ranging from single-subsystem failures to complete spacecraft loss. High-altitude detonations may also generate artificial radiation belts that persist for months, accelerating radiation-induced degradation of satellite components.

High-altitude detonations can also have significant effects on the ground segment of satellite communication systems. A high-altitude EMP may induce damaging currents in user terminals, ground stations, and control facilities over wide geographic areas, potentially disrupting satellite services even where spacecraft remain functional.

During the Cold War, the Soviet Union developed a system that was to be launched into low-Earth polar orbit and then de-orbited for attack with a nuclear warhead ¹, intended in part to circumvent ballistic missile early-warning and defense systems. A south-to-north polar orbit was chosen to avoid the US ballistic missile defences oriented toward the north. ² More recently, a number of experts have warned that two of North Korea’s satellites in polar orbit may carry nuclear warheads designed for a high-altitude electromagnetic pulse attack. ³